The present invention relates to an ink recording apparatus, and particularly to an ink recording apparatus which ejects ink from an ink head onto a medium according to printing data thereby to perform printing.
An ink head used in an ink recording apparatus is characterized in that miniaturization can be facilitated, a high accurate image can be recorded at a high speed, and the image can be recorded on plain paper without requiring special processing. Therefore, the ink recording apparatus is applied to various apparatuses such as a printer, a scanner in-printer (built-in-printer), and the like.
However, the ink ejected from the ink head does not attach onto the whole of the surface of a medium, but a part of ink splashes round and ink mist is produced. In the ink recording apparatus, occurrence of mist, nozzle stain, and mask stain due to this ink mist is not avoided, which obstructs improvement of printing quality. The mist means that the ink which has become misty attaches to other portion than the desired portion thereby to cause difficulty in seeing a print image. The nozzle stain means that the ink which has become misty attaches to a nozzle gradually thereby to drop from the nozzle onto paper. The mask stain means that the ink which has become misty attaches to a mask surface and transfers to the paper, whereby the paper is stained with the ink.
It is said that the mist, the nozzle stain, and the mask stain are caused by static electricity. This static electricity is caused, for example, by friction between paper and a transport roller, and friction between paper and a transport guide. The ink that has been ejected and become misty is caught by this static electricity, and attaches to the paper, the nozzle, and the mask, thereby to cause the mist, the nozzle stain, and the mask stain respectively.
Therefore, many technologies for preventing occurrence of the stains due to static electricity have been proposed. For example, a technology has been proposed in which a charge member that is electrically insulated is provided inside a recording apparatus, the static electricity is generated in the charge member during recording, and ink mist produced during recording is attached to the charged charge member, whereby stains on other points inside the recording apparatus are prevented (refer to JP-A-10-264412).
In the usual ink recording apparatus (ink jet type printer), the stains due to the ink mist can be effectively prevented by measures for static electricity.
However, according to the investigation by the present inventors, in a printer of a type in which printing (recording) is performed while transporting paper (medium) at a high speed (hereinafter, referred to as a high-speed type), such as a scanner in-printer, it has been found that the following characteristic problems are produced.
Namely, in the high-speed type printer, the stains due to the ink mist cannot be effectively prevented only by the measures for static electricity, and it has been found that the stains due to the ink mist are caused not only by the static electricity but also by blow produced by transport of the paper (medium) (hereinafter, referred to as transport blow). Namely, in case that the paper (medium) is transported at a high speed, the transport blow is produced with this paper transport, and a droplet (shot) of the ink that has been ejected and become misty flows by this transport blow and attaches to the paper, the nozzle and the mask, whereby the mist, the nozzle stain, and the mask stain are caused respectively. Further, in the high-speed type printer, since the paper (recorded medium) is transported at a high speed, a large amount of static electricity is also produced. Therefore, it is been found that measures for static electricity which does not conflict with the measures for transport blow must be taken.